BHN Reality

[Latigo]

I have around 550 pounds of early 70's vintage Wheel Weights, and the nominal BHN is average 10 across all of the samples from the different buckets. If I'm beginning with a 20 pound pot, taken to 1150 degrees and adding a % of pulverized Anthimony, how high would you take the BHN?

My first useable batch ended up at 28. The first batch was too high.
I need to do repeatable 2,500fps in a k31 rifle.

How high would you take it assuming that the BHN is not just a case hardening, but all the way through the projectile?

Latigo

[garandsrus]

Hi,

I would not take the lead to 1150 degrees! Most folks melt and cast at 650-750. Add an alloy that already contains antimony, such as linotype.

John

[Latigo]

John, Anthimony requires that temp to melt and mix. What I have is 10 pounds of Anthimony in the original "rock" form. We pulverize it to make it mixable.
Once that temp is reached and the Anthimony is melted and mixed, we back it off down to 700. When we restart the pot we have to up to 1150, mix and then back off again. No other way to do it that I've ever heard, and I definitley don't want to just let 550 pounds of lead sit there unused.

Secondly, to reach a specific BHN I need to stay with the correct % Anthimony added every time. I don't want to mix, cast, test, add more, mix cast, test and repeat that process until I'm at the correct BHN for those velocities. It would take forever and endless controlo groups. So, that being said........ If I've been doing it incorrectly, please educate me. So far its working great. My question was about a BHN that would take me to those velocities without being too hard for practical application.

Does anyone here do a through and through BHN factor, or is it mostly just case hardening you do? It is working, but if I can be somewhat lower and keep a clean barrel at 2,500fps, I'd sure like to know. Has anyone run tests at that velocity with repeatable results at a given BHN factor?

Thanks for the help, or education.

Latigo

[felix]

BHN is a valid indicator only for something that is made from 100 percent reliable components, and only if you are trying to mix them to make a repeatable alloy. By changing just one alloy component percentage will change the way the resulting boolits shoot. Not only that, each boolit style and diameter will need a specific amount and powder speed in the very same gun to make the BHN valid as a repeatable boolit alloy parameter. In general, I say BHN is just another indicator which does not help in the accuracy department because the feed stock for the alloy is up in the air almost ALWAYS. ... felix

[oso]

From some old threads:
You can dissolve antimony pieces into a lead + tin melt at normal casting temps as the antimony forms an inter-metallic compound with the tin. The trick is to submerge the antimony chunks in the melt or it just floats on the surface. I perforated the bottom of a can that fits the pot and made a wire handle to move it up and down for agitation while dissolving. I wouldn't mess with antimony dust.
To melt antimony I've used a charcoal furnace with blower - more trouble than it was worth.
also:
Antimony will dissolve in molten lead if some tin is present (forming an inter-metalic compound with the antimony, the tin facilitates dissolution.) High temps and special flux are not required; I just submerge the antimony in the lead tin (1% tin will do) alloy and move the submerging mesh up and down.
I have also melted antimony and it was more trouble than it was worth.

There are other ways to skin this cat (the search function works.)
BHN would not be my major concern with your intended application, but optimal boolit fit and paper patching work for me.

[Latigo]

Hooo Doggies. :sad: Thanks Felix. Ok, so I'll do some in depth research here before going any further. I've been depending on the WWs to be about the same across the board. The first useable mixture did allow me to chrono a nominal 2,450fps, but since its sub zero here a lot of the time for now I haven't been able to do any real accuracy testing. With a 174 spire point at 100 yards and 4064 powder I'm at about 2.85" with 5 shots. The first ones were swaged, hBN impact coated and then gas checked.

We do have a Shoot Shed with firing ports but the outside temps have been in the teens at best and even lower. I'll probably ingot the balance and wait till spring now before going any further.

Latigo

And thanks, OSO! I hadn't seen that before I posted.

[geargnasher]

Latigo, I was going to mention the tin thing but someone else already explained it well.

Now, for the "real world" dope on bhn and ternary alloys: Unless you're casting under laboratory conditions you will get swings of 2-3 points from the mean just by having a 50* swing in MOULD temperature. I know because I have tested this. Antimony makes lead alloy very touchy with cooling rate, and the hotter the mould the harder your boolits will be after they age-harden The exact composition of an alloy has little effect on it's final BHN, just because you have an exact "hardball" alloy for example (92Pb/6Sb/2Sn) doesn't mean it will always be 16 BHN. If you water-quench it, it will be 25 or more after a week, if you air cool it from a 375* mould it might be about 16, and if you air cool it from a 300* mold it might be 11. Boolits cast at the start of a session won't be the same as boolits cast at the end of a session.

Gear

[KYCaster]

Latigo, welcome to the Cast Boolits forum. I hope we can help you find the answers you're looking for.

Adding Antimony doesn't require high temps. It can easily be done at normal casting temp. The process has been described here in detail by at least three different people. Search for "antimony" in posts by 44man and Run5run.

Case hardening? Heat treating lead alloys doesn't result in a uniformly hard layer surrounding a uniformly soft core. Any difference between surface hardness and core hardness will be a gradual change and is simply because it is impossible to reduce the temp of the core as fast as the surface. Since lead alloys work soften, any attempt to expose the core for hardness testing will destroy the effects of the heat treat. The larger the boolit diameter, the more likely there will be a significant difference in the quench rate from surface to core, therefore, the greater the chance of the core being softer than the surface.

2500 fps? We've been discussing this for years and have not yet reached a consensus. It would probably take several months just to scratch the surface and in the end you just have to figure it out for yourself. ("endless control groups"[smilie=1:)

Personally, I've had very good results with ACWW up to 2200 fps in various 30 and 35 cal rifles. I haven't gone much beyond that and I have a few more things to explore before I try heat treating for more hardness.

Another thing to keep in mind...linotype alloy at 22 BHN and Lyman #2 heat treated to 22 BHN will have vastly different terminal performance. Which one is best depends on the individual situation.

Bottom line is, nobody can tell you what will work in your situation. All we can do is answer specific questions and relate what has worked for us.

Good luck
Jerry

[Latigo]

Thank you very much. Now I'm going to shut up and read this board, which I should have done to begin with.
I got my Anthimony melting temps from Lyman, and I've been pulverising the daylights out of some of the smaller rocks.
Truly a great board. I intend to learn a few things before spring.
Thanks again!

Latigo

[1Shirt]

Just to add my 2 cents worth. I like hard blts, in the Lino bh level, as long as they are large enough for the bore. I like wheel weights, about 3/4 of the melt, a cup of Mag shot, and a little tin, and I water drop everything. Usually end up on the +side of 22BH.
Have a cabin tree hardness tester, and if you are really wanting to work on determining BH, suggest you consider a tester of some kind as well.
Good Luck!
1Shirt!:coffeecom

[Latigo]

Thanks! We have a Saeco and a Lee.

[Suo Gan]

If I were you, I would sell the antimony here and water drop the boolits. A lot less hassle to get you where you want to be.

[cbrick]

1150 degrees, wow. You must be using a gas fired pot, I doubt any of my electric pots would come close to that but I confess to never have tried, 725 degrees is hot casting for me. Plus, what thermometer are you using? My casting thermometers go to 1,000 degrees but none have ever been anything close to that. Tin up to about 2% is very beneficial in a Pb - Sb alloy but past 750 degrees Sn will loose it's ability to inhibit oxidation and the Sn itself will oxidize very rapidly, the higher the temp the faster the Sn oxidation. Tin or not, any metal in your alloy will oxidize rapidly at 1150 degrees.

Roto Metals Super Hard alloy (used for blending with a base alloy, not casting) is 30% Sb - 70% Pb and melts at 550 degrees and blends easily with the base alloy.

I should caution you against attempting to reach a BHN of 25+ through the use of antimony if your intended purpose is any expansion at all for hunting bullets, you'll get none. What you will get is an extremely brittle bullet.

Also curious about the BHN testing method your using to get 10 BHN with early weights. Everything I've read about mid 70's and earlier WW's says a much higher Sb percentage than what is common in today's weights and my recent weights run about 11 BHN (with 2% added Sn and air cooled). I wish I had a supply of early weights to do some testing of this myself but I've never run across any so I go with the conventional wisdom on this.

Rick

[GLL]

I also use the RotoMetals Super Hard 30%Sb/70%Pb alloy Rick mentioned. It is not expensive and saves time and effort plus you know the exact composition of your resultant "blended" alloy.

Jerry

[cajun shooter]

I first started using WW's in the 70's and I did not even know what BHN was at the time. I was shown by my mentor and he never said anything. I was casting all revolver rounds from 9MM, 38,357, 41 mag, 44 spl and 44 mag , 45 ACP. I can only say this and that is the bullets that I cast today are as close to 20-1 that I can do. These test out in the area of 10 BHN. I have found this to be a almost perfect bullet for my Black Powder shooting. Now I shot IHMSA and to me the recovered bullets of today's shooting look the same as the recovered bullets of the 70's. That means that they are in close to being in the same range as those from the 70's. I can only speak of Louisiana and the WW's here that I test now all read about 9.5 BHN. I fully realize that this is in no way a correct way to judge a hardness test but merely a observation on my part.

[fredj338]

I would be concerened about lead vaporizing @ temps above 1000deg. There just isn't amy point in trying to add pulverized antimony, when it is more easily added using hardened shot or Linotype, etc.